
//cnpm i xlsx -S
/* eslint-disable */
import XLSX from 'xlsx'

export default {


    // 将一个sheet转成最终的excel文件的blob对象，然后利用URL.createObjectURL下载
    sheet2blob(sheet, sheetName) {
        sheetName = sheetName || 'sheet1';
        var workbook = {
            SheetNames: [sheetName],
            Sheets: {}
        };
        workbook.Sheets[sheetName] = sheet;
        // 生成excel的配置项
        var wopts = {
            bookType: 'xlsx', // 要生成的文件类型
            bookSST: false, // 是否生成Shared String Table，官方解释是，如果开启生成速度会下降，但在低版本IOS设备上有更好的兼容性
            type: 'binary'
        };
        var wbout = XLSX.write(workbook, wopts);
        var blob = new Blob([s2ab(wbout)], {type:"application/octet-stream"});
        // 字符串转ArrayBuffer
        function s2ab(s) {
            var buf = new ArrayBuffer(s.length);
            var view = new Uint8Array(buf);
            for (var i=0; i!=s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
            return buf;
        }
        return blob;
    },
    /**
     * 通用的打开下载对话框方法，没有测试过具体兼容性
     * @param url 下载地址，也可以是一个blob对象，必选
     * @param saveName 保存文件名，可选
     */
    openDownloadDialog(url, saveName) {
        if(typeof url == 'object' && url instanceof Blob)
        {
            url = URL.createObjectURL(url); // 创建blob地址
        }
        var aLink = document.createElement('a');
        aLink.href = url;
        aLink.download = saveName || ''; // HTML5新增的属性，指定保存文件名，可以不要后缀，注意，file:///模式下不会生效
        var event;
        if(window.MouseEvent) event = new MouseEvent('click');
        else
        {
            event = document.createEvent('MouseEvents');
            event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
        }
        aLink.dispatchEvent(event);
    },

    export (list, fileName) {
        var sheet = XLSX.utils.json_to_sheet(list);
        this.openDownloadDialog(this.sheet2blob(sheet), fileName);
    },


    read (file) {
        return new Promise((resolve, reject) => {
            const reader = new FileReader();
            reader.readAsBinaryString(file);
            reader.onload = (e) => {
                const data = e.target.result;
                const zzexcel = XLSX.read(data, {
                    type: 'binary'
                });
                const result = [];

                // for (let i = 0; i < zzexcel.SheetNames.length; i++) {
                //     const newData = XLSX.utils.sheet_to_json(zzexcel.Sheets[zzexcel.SheetNames[i]]);
                //     result.push(...newData)
                // }
                // 只取第一个Sheet
                const newData = XLSX.utils.sheet_to_json(zzexcel.Sheets[zzexcel.SheetNames[0]]);
                result.push(...newData)
                resolve(result)
            }
        })
    }
}
